Kinematic comparison of baseball throwing motions in relation to the trunk and throwing arm among various types of player positions

Abstract

  The purpose of the present study was to clarify kinematic differences in baseball throwing motions among various types of player positions—pitcher, catcher and infielder—based on kinematic data reported in previous studies. A total of 20 articles including 17 pitching studies, 2 catcher's delivery studies and 1 infielder's delivery study were investigated mainly with regard to trunk and throwing arm kinematics. Since there no kinematic data were available for the trunk and throwing arm of the catcher, only release parameters (i.e., ball speed, release angle, and height of release) and the durations of the 4 throwing phases (i.e., step, stride, arm cocking, and arm acceleration) were compared between the catcher and the players at other positions. The characteristic differences observed for each throwing motion were as follows: Ball speed was greater for the pitcher than for other positions. Although step phase was shorter for the catcher than for the infielder, stride phase was shorter in the latter. Both arm cocking and acceleration phases were shorter for the pitcher than for players at other positions. At the instant of stride foot contact, trunk backward twist and elbow extension angles were larger for the pitcher than for the infielder, and the pelvis backward rotation angle was smaller for the former. At the instant of ball release, the upper trunk forward tilt, upper trunk leftward tilt, and trunk forward twist angles were larger for the pitcher than for the infielder. Maximum elbow flexion and shoulder horizontal abduction angles were larger for the pitcher than for the infielder, whereas the maximum shoulder external rotation angle was smaller for the former. Although there were no marked differences in the maximum upper trunk and pelvis forward rotation angular velocities between the pitcher and the infielder, their times of occurrence arose in the early phase of throwing in the pitcher in comparison with the infielder. These results provide evidence of possible ways in which the throwing performance of players in various positions can be improved.